1. Field of the Invention
This invention relates to methods and apparatus used in an orthodontic treatment program to apply a composition to external areas of the patient's teeth.
2. Description of the Related Art
Orthodontic treatment involves movement of malpositioned teeth to improved locations. Orthodontic treatment can greatly enhance the aesthetic appearance of the patient, especially in areas near the front of the oral cavity. Orthodontic treatment can also improve the patient's occlusion so that the teeth function better with each other during mastication.
One type of common orthodontic treatment program includes the use of a set of small slotted appliances known as brackets. The brackets are affixed to the patient's teeth and an archwire is placed in the slot of each bracket. The archwire forms a track to guide movement of the teeth to desired positions. End portions of the archwire are often captured in buccal tube appliances that are affixed to the patient's molar teeth.
Many orthodontic appliances are directly bonded to the patient's tooth enamel by an adhesive composition. The adhesive composition may be a photocurable adhesive, which begins to cure upon exposure to light in certain ranges of wavelength. Another common type of orthodontic bonding composition is provided as two initially separate components that begin to cure once mixed together.
Regardless of the type of bonding composition used by the practitioner, it is important that bond failures do not occur and that the appliances remain securely fixed to the teeth for the intended length of treatment time. If, for example, one or more of the appliances detach from the teeth during the course of treatment, the progress of treatment is often interrupted and the patent should then return to the practitioner's office for reattachment or replacement of the detached appliances. Bond failures of orthodontic appliances represent a significant nuisance in terms of time and expense for both the practitioner and the patient that should be avoided if at all possible.
As a consequence, careful preparation of the appliances and the patient's teeth is an important task prior to the appliance bonding procedure. Preparation of the patient's teeth usually includes the steps of etching and priming the teeth following tooth cleaning. In one procedure, the practitioner applies an etchant such as phosphoric acid to each tooth using, for example, a small brush or swab. Next, the teeth are rinsed of the etchant and dried. The practitioner then applies a primer composition to each tooth, again using, for example, a small brush or swab. Alternatively, following tooth cleaning, the practitioner may choose to use a single composition that serves as both an etchant and a primer.
In any case, however, it is usually preferred to apply the etchant and primer compositions, or the combination etchant/primer composition, to only those areas of the teeth that will be adjacent the base of the appliance once the appliance has been bonded to the teeth. Etchant compositions are acidic and may irritate a patient's gingival tissue. For that reason, it is desired to carefully apply the etchant composition in a controlled manner with a small applicator so that contact with the gingival tissue is avoided.
Additionally, some patients may have an allergic reaction or develop a sensitivity to certain components present in orthodontic primers. Consequently, it is important to also carefully apply the primer to the patient's teeth in order to avoid contact of the primer with gingival tissue. It is also important to avoid placing primer in interproximal regions of the dental arch because the primer may hinder movement of the teeth to desired positions once the primer has hardened.